Lubricating composition

ABSTRACT

A lubricating oil composition having improved anti-oxidation properties comprising: a base oil comprising a Fischer-Tropsch derived base oil; and an organic dye compound.

This non-provisional application claims priority from U.S. Provisional Application Ser. No. 61/836331 filed Jun. 18, 2013 which is hereby incorporated by reference in its entirety.

The present invention relates to a lubricating composition, in particular a lubricating composition having improved oxidation stability, foaming performance, air release, demulsibility, filterability, corrosion reduction, and deposit reduction.

As is disclosed in for example D. J. Wedlock et al., “Gas-to-Liquids Base Oils to assist in meeting OEM requirements 2010 and beyond”, presented at the 2nd Asia-Pacific base oil Conference, Beijing, China, 23-25 Oct. 2007, the use of Fischer-Tropsch derived base oils in lubricating compositions such as engine oils, transmission fluids, and industrial lubricants can result in various performance benefits. Examples of performance benefits by the use of Fischer-Tropsch derived base oils mentioned in the above article include: improved oxidation properties, improved engine cleanliness, improved wear protection, improved emissions and improved after-treatment device compatibility. Also the Fischer-Tropsch base oils allow for the formulation of low-viscosity energy conserving formulations.

Fischer-Tropsch derived base oils are highly paraffinic API group III base oils (API Base Oil Interchangeability Guidelines) exhibiting very good cold flow properties, high oxidative stability, and high viscosity indices. However, due to the high paraffin content the solvency of the base oils is generally low, resulting in incompatibility with other lubricant components and additives.

Fischer-Tropsch base oils may have relatively low solvency. As used herein the term “solvency” in relation to a base oil means the ability of that base oil to dissolve various performance additives or, for that matter, dissolve any component that may potentially “desolvate” and form solids or a second liquid phase, including oxidation byproducts. Thus, in one embodiment, it would be desirable to develop lubricating compositions having increased solvency at the same time as exhibiting the other performance benefits mentioned above, in particular improved oxidation stability and reduced piston deposits.

One or more of the above or other objects can be obtained by a lubricating oil composition comprising:

-   (a) a base oil selected from Group III base oils, Group IV     polyalphaolefins, or a combination thereof; and -   (b) between 0.0001 and 0.001 wt % of an organic dye compound.

In certain embodiments, the lubricating oil composition can include a solvent in which the organic dye compounds can be dissolved. In certain embodiments, the lubricating oil composition can further include an antioxidant, wherein the antioxidant can be selected from aminic antioxidants, phenolic antioxidants, and mixtures thereof. In certain embodiments, the lubricant composition can further include one or more detergent compounds having a TBN (total base number equivalent, as determined by ASTM D2896) in the range of from 0-400.

It has surprisingly been found that the lubricating compositions according to the present invention exhibit improved oxidation stability, foaming performance, air release, demulsibility, filterability, corrosion reduction, and deposit reduction.

The lubricant composition described herein can find a variety of uses as a lubricant, including but not limited to, lubrication of transmissions, turbines, air compressors, hydraulic systems, and the like.

The base oil used in the lubricating composition according to the present invention is selected from a Group III base oil, a polyalphaolefin, and mixtures thereof. The base oil used in the present invention may conveniently comprise mixtures of one or more Group III base oils and/or polyalphaolefins, thus, according to the present invention, the term “base oil” may refer to a mixture containing more than one base oil. Suitable base oils for use in the lubricating oil composition of the present invention are Group III mineral base oils, Group IV poly-alpha olefins (PAOs), Group III Fischer-Tropsch derived base oils, and mixtures thereof.

By “Group III” and “Group IV” base oils in the present invention are meant lubricating oil base oils according to the definitions of American Petroleum Institute (API) for category III and IV. These API categories are defined in API Publication 1509, 15th Edition, Appendix E, April 2002.

Fischer-Tropsch derived base oils are known in the art. By the term “Fischer-Tropsch derived” is meant that a base oil is, or is derived from, a synthesis product of a Fischer-Tropsch process. A Fischer-Tropsch derived base oil may also be referred to as a GTL (Gas-To-Liquids) base oil. Suitable Fischer-Tropsch derived base oils that may be conveniently used as the base oil in the lubricating composition of the present invention include those, for example, disclosed in EP 0 776 959, EP 0 668 342, WO 97/21788, WO 00/15736, WO 00/14188, WO 00/14187, WO 00/14183, WO 00/14179, WO 00/08115, WO 99/41332, EP 1 029 029, WO 01/18156 and WO 01/57166.

Typically, the aromatics content of a Fischer-Tropsch derived base oil, suitably determined by ASTM D 4629, will be less than about 1 wt. %, alternatively less than about 0.5 wt. % or in alternate embodiments, less than about 0.1 wt. %. Suitably, the base oil has a total paraffin content of at least about 80 wt. %, alternatively at least about 85 wt. %, alternatively at least about 90 wt. %, alternatively at least about 95 wt. %, or, in certain embodiments, at least about 99 wt. %. The Fischer-Tropsch derived base oil suitably has a saturates content (as measured by IP-368, ASTM D2007, ASTM D7419, or any other chromatographic method that will yield similar results) of greater than about 98 wt. %, alternatively greater than about 99 wt. %, or alternatively greater than about 99.5 wt. %. The Fischer-Tropsch derived base oil can further include a maximum n-paraffin content of about 0.5 wt. % and naphthenic compound content of from 0 to less than 20 wt. %, alternatively from about 0.5 to 10 wt. %, alternatively from about 1-5 wt. %, or alternatively from about 5-10 wt. %.

Typically, the Fischer-Tropsch derived base oil or base oil blend has a kinematic viscosity at 100° C. (as measured by ASTM D 7042) in the range of from 1 to 35 mm²/s (cSt), alternatively from 1 to 25 mm²/s (cSt), alternatively from 2 to 20 mm²/s (cSt), or alternativley from 2 mm²/s to 12 mm²/s. The Fischer-Tropsch derived base oil can have a kinematic viscosity at 100° C. (as measured by ASTM D 7042) of at least 2.5 mm²/s, alternativley at least 3.0 mm²/s (e.g., “GTL 3”. In certain embodiments of the present invention, the Fischer-Tropsch derived base oil can have a kinematic viscosity at 100° C. of not greater than 5.0 mm²/s, alternatively not greater than 4.5 mm²/s, alternatively not greater than 4.2 mm²/s (e.g., “GTL 4”). In certain embodiments of the present invention, the Fischer-Tropsch derived base oil has a kinematic viscosity at 100° C. of not greater than 8.5 mm²/s, alternatively not greater than 8 mm²/s (e.g., “GTL 8”). Other grades of GTL products would also be possible, based upon the specific distillation process utilized to produce the GTL product.

Further, the Fischer-Tropsch derived base oil can have a kinematic viscosity at 40° C. (as measured by ASTM D 7042) of from 10 to 100 mm²/s (cSt), alternatively from 15 to 50 mm²/s, alternatively from 50 to 80 mm²/s, alternatively greater than 100 mm²/s.

Also, in certain embodiments, the Fischer-Tropsch derived base oil can have a pour point (as measured according to ASTM D 5950) of less than about −10° C., alternatively less than about −20° C., alternatively less than about −30° C., alternativley less than about −40° C., and alternatively less than about −45° C.

The flash point (as measured by ASTM D92) of the Fischer-Tropsch derived base oil can be greater than 120° C., alternatively greater than 140° C.

The Fischer-Tropsch derived base oil can have a viscosity index (according to ASTM D 2270) in the range of from about 100 to 200. Alternativley, the Fischer-Tropsch derived base oil can have a viscosity index of at least 125, alternatively at least 130. In certain embodiments, the viscosity index is less than 180, alternatively less than 160, alternatively less than 150.

In the event the Fischer-Tropsch derived base oil contains a blend of two or more Fischer-Tropsch derived base oils, the above values apply to the blend of the two or more Fischer-Tropsch derived base oils.

Poly-alpha olefin base oils (PAOs) and their manufacture are well known in the art. In certain embodiments, the poly-alpha olefin base oils used in the lubricating compositions of the present invention may be derived from linear C₂ to C₃₂, preferably C₆ to C₁₆, alpha olefins. Alternatively, feedstocks for said poly-alpha olefins can be 1-octene, 1-decene, 1-dodecene and 1-tetradecene.

In certain embodiments, the base oil as used in the lubricating composition can include a first GTL base oil, and may optionally include one or more of the oils selected from PAO, or Group I, II, III or V base oils.

In certain embodiments, it may be preferable to use a Fischer-Tropsch derived base oil instead of a PAO base oil, in view of the high cost to manufacture PAOs. Thus, preferably, the base oil contains more than 50 wt. %, preferably more than 60 wt. %, more preferably more than 70 wt. %, even more preferably more than 80 wt. %, and most preferably more than 90 wt. % of a Fischer-Tropsch derived base oil. In an alternate embodiment, not more than 5 wt. %, alternatively not more than 2 wt. %, of the base oil is not a Fischer-Tropsch derived base oil. In certain preferred embodiments, 100 wt % of the base oil is based on one or more Fischer-Tropsch derived base oils.

Preferably the base oil or base oil blend that includes the Fischer-Tropsch derived base oil has a kinematic viscosity at 100° C. of between 2 and 35 cSt, alternatively between 2 and 10.5 cSt (according to ASTM D 445).

In addition to the Group III base oil and/or polyalphaolefin base oil, the lubricating composition may include one or more other types of mineral derived or synthetic base oils, including Group I, II, IV and V base oils according to the definitions of American Petroleum Institute (API). These API categories are defined in API Publication 1509, 15th Edition, Appendix E, July 2009.

In certain embodiments, the total amount of base oil that is incorporated in the lubricating composition of the present invention is preferably an amount in the range of from 60 to 99 wt. %, alternatively an amount in the range of from 65 to 90 wt. %, and in certain preferred embodiments, in an amount in the range of from 70 to 85 wt. %, with respect to the total weight of the lubricating composition.

The lubricating oil composition also includes an oil soluble organic dye. The organic dye can include functional groups that serves as chromophores that absorb and transmit wavelengths in the visible spectrum. Exemplary dyes that can be used in the lubricating oil composition of the present invention can generally be placed in two catagories based upon the solvent volatility: low flash dyes and high flash dyes. Exemplary low flash dyes can include those sold under the tradename “Unisol”, such as Unisol Blue A (United Color Manufacturing, Inc.), and dyes sold under the tradename “Automate”, such as Automate Red GXS (Dow Chemical Company). Exemplary high flash dyes can includes those sold under the tradename “Unisol”, such as Unisol Blue AHF (United Color Manufacturing, Inc.) and dyes sold under the tradename “Novalube”, such as Novalube Yellow 326.

In certain embodiments the organic dyes can be first dissolved in an organic solvent prior to being added to the base oil. Exemplary organic solvents can include hydrocarbon solvents having relatively low flash points, such as xylene, dimethylbenzene, ethylbenzene, and the like. Exemplary low flash solvents typically have a flash point of less than about 200° F. Exemplary high flash solvents typically have a flash point of greater than about 200° F. Other exemplary organic solvents can include petroleum distillates, such as kerosene. In certain embodiments, the amount of solvent that can be added to the organic dye can be between 10 and 90% by weight, alternatively between about 10 and 30% by weight, alternatively between about 30 and 60% by weight, alternatively between about 60 and 90% by weight.

The organic dyes can be present in an amount of between about 0.0001 wt. % and 0.001 wt. % as measured relative to the total weight of the lubricant composition, alternatively between about 0.0001 wt. % and 0.0005 wt. %, alternatively between about 0.0005 wt. % and 0.001 wt. %. In certain embodiments, two or more organic dyes can be present in the lubricant composition, wherein the total concentration of the organic dyes is between about 0.0001 wt. % and 0.001 wt. %, as measured relative to the total weight of the lubricant composition, alternatively between about 0.0001 wt. % and 0.0005 wt. %, alternatively between about 0.0005 wt. % and 0.001 wt. %.

Optionally, the lubricating oil compositions of the present invention can also include a solvency booster. As used herein, the term “solvency booster” means a component which enhances the solvency of the Group III/PAO base oil with respect to certain additives that are included in the formulation. The use of a solvency booster in the lubricating composition of the present invention can be particularly useful when the base oil is selected from a Fischer-Tropsch derived base oil.

In certain embodiments, the solvency booster is present in an amount of 30 wt % or less, preferably 20 wt % of less, more preferably 15 wt % or less, by weight of the lubricating oil composition. The solvency booster is preferably present at a level of 1 wt % or more, more preferably 3 wt % or more, even more preferably 5 wt % or more, by weight of the lubricating oil composition. Alternatively, the solvency booster is present in an amount of between about 1 and 30 wt %, alternatively in an amount of between about 2 and 20 wt %, or alternatively in an amount between about 5 and 15 wt %.

Compounds suitable for use as a solvency booster can be selected from alkylated aromatic compounds, naphthenic base oils, ester base oils, and mixtures thereof.

Preferred alkylated aromatic compounds for use as a solvency booster herein can include alkylated benzenes, alkylated anthracenes, alkylated phenanthrenes, alkylated biphenyls, and alkylated naphthalenes and mixtures thereof.

Alkylated naphthalenes may be produced by any suitable means known in the art, from naphthalene itself or from substituted naphthalenes which may contain one or more short chain alkyl groups having up to about eight carbon atoms, for example methyl, ethyl, and propyl. Suitable alkyl-substituted naphthalenes include alphamethylnaphthalene, dimethylnaphthalene, and ethylnaphthalene. Naphthalene itself is especially suitable since the resulting mono-alkylated products have better thermal and oxidative stability than the more highly alkylated materials. Suitable alkylated naphthalene lubricant compositions are described in U.S. Pat. No. 3,812,036, and U.S. Pat. No. 5,602,086. The preparation of alkylnaphthalenes is further disclosed in U.S. Pat. No. 4,714,794.

The alkylated aromatic compound for use herein can be selected from alkylbenzene compounds, alkylnaphthalene compounds, and mixtures thereof.

The alkylaromatic component preferably has a kinematic viscosity at 100° C. in the range of from 3 to 12 mm²/s, more preferably in the range of from 3.8 to 7 mm²/s. The viscosity index of the alkylaromatic component is above 40, preferably at or above 70.

An exemplary alkylated aromatic compound for use herein is an alkylnaphthalene compound. Examples of commercially available alkylnaphthalene compounds are those under the tradename NA-Lube (King Industries), such as NA-Lube KR 008, NA-Lube KR019, and the like, and those under the tradename Mobil MCP (ExxonMobil).

Examples of commercially available alkyl benzenes include those available under the tradename Fusyn-22 (Formosan), those available under the tradename Janex HAL (Janex), and those available under the tradename ZEROL (Shreive Chemical Products, Inc. (SCP)).

Suitable naphthenic base oils for use as a solvency booster herein includes naphthenic base oils having low viscosity index (VI), typically between about 40-80, and a low pour point, for example, a temperature of less than −20° C. Such base oils can be produced from feedstocks rich in naphthenes and low in wax content. There is no particular limitation on the type of mineral-derived naphthenic base oil which can be used in the base oil composition herein. Any mineral-derived naphthenic base oil which is suitable for use in a lubricating oil composition can be used herein. Naphthenic base oils are defined as Group V base oils according to API. Such mineral-derived base oils can be obtained by refinery processes starting from naphthenic crude feeds. Mineral-derived naphthenic base oils for use herein preferably have a pour point of below −20° C. and a viscosity index of less than 70. Such base oils can be produced from feedstocks rich in naphthenes and low in wax content. Mineral-derived naphthenic base oils are well known and described in more detail in “Lubricant base oil and wax processing”, Avilino Sequeira, Jr., Marcel Dekker, Inc, New York, 1994, ISBN 0-8247-9256-4, pages 28-35. Methods of manufacture of naphthenic base oils can be found in “Lubricants and Lubrication (Second, Completely Revised and Extended Edition)”, published by Wiley-VCH Verlag GmbH & Co. KgaA, Chapter 4, pages 46-48.

An example of a suitable naphthenic base oil for use as a solvency booster herein is that commercially available under the tradename KN4006 (China National Petroleum Corporation). Other examples of suitable naphthenic base oils for use as a solvency booster herein include those available under the tradenames Hydrocal, Hydrosol and HR Tufflo (Calumet Specialty Products), and those commercially available under the tradename Nynas (Nynas Oil Company).

Suitable esters for use as a solvency booster herein include natural and synthetic esters such as diesters and polyol esters. An example of a suitable ester for use as a solvency booster herein is the saturated polyol ester commercially available under the tradename Priolube 3970 (Croda International PLC). Other suitable esters for use as a solvency booster herein include those available under the tradename Radialube (Oleon), those available under the tradename Emery (from Emery) and those available under the tradename Esterex (ExxonMobil Chemical).

The lubricating oil compositions of the present invention can include one or more detergent compounds having a TBN (total base number equivalent, as determined by ASTM D2896) of between about 0 and 400. In certain embodiments, the detergent compound can include one or more alkaline earth metal salicylate.

Suitable alkaline earth metal salicylates include calcium, magnesium and barium salicylates, and mixtures thereof, preferably calcium salicylates.

The lubricating oil compositions of the present invention preferably include from 0.01 wt % to 9 wt %, more preferably from 1 wt % to 6 wt %, even more preferably from 3.5 wt % to 5.5 wt %, of a detergent, by weight of the lubricating oil composition.

The level of an alkaline earth metal salicylate having a TBN in the range of from 150 to 250 is preferably in the range of 0.01 wt % to 5 wt %, more preferably from 1 wt % to 3 wt %, by weight of the lubricating oil composition.

In certain embodiments, the detergent can be an alkaline earth metal salicylate having a TBNE (total base number equivalent, as determined by ASTM D2896) in the range of from 250 to 400, and is preferably in the range of 0.01 wt % to 3 wt %, more preferably from 1 wt % to 2 wt %, by weight of the lubricating oil composition.

In certain embodiments, the lubricating oil compositions of the present invention can include one or more anti-oxidants. Suitable anti-oxidants for use herein include phenolic antioxidants and/or aminic antioxidants.

In one embodiment, said antioxidants are present in an amount in the range of from 0.1 to 5.0 wt. %, preferably in an amount in the range of from 0.3 to 3.0 wt. %, and more preferably in an amount of in the range of from 0.5 to 1.5 wt. %, based on the total weight of the lubricating oil composition.

Examples of aminic antioxidants which may be conveniently used include alkylated diphenylamines, phenyl-α-naphthylamines, phenyl-β-naphthylamines and alkylated α-naphthylamines

Exemplary aminic antioxidants include dialkyldiphenylamines, such as p,p′-dioctyl-diphenylamine, p,p′-di-α-methylbenzyl-diphenylamine, and N-p-butylphenyl-N-p′-octylphenylamine, monoalkyldiphenylamines, such as mono-t-butyldiphenylamine and mono-octyldiphenylamine, bis(dialkylphenyl)amines, such as di-(2,4-diethylphenyl)amine and di(2-ethyl-4-nonylphenyl)amine, alkylphenyl-1-naphthylamines, such as octylphenyl-1-naphthylamine and n-t-dodecylphenyl-1-naphthylamine, 1-naphthylamine, arylnaphthylamines, such as phenyl-1-naphthylamine, phenyl-2-naphthylamine, N-hexylphenyl-2-naphthylamine and N-octylphenyl-2-naphthylamine, phenylenediamines, such as N,N′-diisopropyl-p-phenylenediamine and N,N′-diphenyl-p-phenylenediamine, and phenothiazines, such as phenothiazine and 3,7-dioctylphenothiazine.

Preferred aminic antioxidants include those available under the following trade designations: “Sonoflex OD-3” (Seiko Kagaku Co.), “Irganox L-57” (Ciba Specialty Chemicals Co.) and phenothiazine (Hodogaya Kagaku Co.).

Exemplary phenolic antioxidants that may be used include C7-C9 branched alkyl esters of 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-benzenepropanoic acid, 2-t-butylphenol, 2-t-butyl-4-methylphenol, 2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol, 2,4-dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-4-alkylphenols such as 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol and 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-alkoxyphenols such as 2,6-di-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-ethoxyphenol, 3,5-di-t-butyl-4-hydroxybenzylmercaptooctylacetate, alkyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionates such as n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, n-butyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and 2′-ethylhexyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-d-t-butyl-α-dimethylamino-p-cresol, 2,2′-methylenebis(4-alkyl-6-t-butylphenol) such as 2,2′-methylenebis(4-methyl-6-t-butylphenol, and 2,2-methylenebis(4-ethyl-6-t-butylphenol), bisphenols such as 4,4′-butylidenebis(3-methyl-6-t-butylphenol, 4,4′-methylenebis(2,6-di-t-butylphenol), 4,4′-bis(2,6-di-t-butylphenol), 2,2-(di-p-hydroxyphenyl)propane, 2,2-bis(3,5-di-t-butyl-4-hydroxyphenyl)propane, 4,4′-cyclohexylidenebis(2,6-t-butylphenol), hexamethyleneglycol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], triethyleneglycolbis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate], 2,2′-thio-[[diethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 3,9-bis{1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxylethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, 4,4′-thiobis(3-methyl-6-t-butylphenol) and 2,2′-thiobis(4,6-di-t-butylresorcinol), polyphenols such as tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)-butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis-[3,3′-bis(4′-hydroxy-3′-t-butylphenyl)butyric acid]glycol ester, 2-(3′,5′-di-t-butyl-4-hydroxyphenyl)methyl-4-(2″,4″-di-t-butyl-3″-hydroxyphenyl)methyl-6-t-butylphenol and 2,6-bis(2′-hydroxy-3′-t-butyl-5′-methylbenzyl)-4-methylphenol, and p-t-butylphenol-formaldehyde condensates and p-t-butylphenol-acetaldehyde condensates.

Phenolic antioxidants include those available under the following trade designations: “Irganox L-135” (Ciba Specialty Chemicals Co.), “Yoshinox SS” (Yoshitomi Seiyaku Co.), “Antage W-400” (Kawaguchi Kagaku Co.), “Antage W-500” (Kawaguchi Kagaku Co.), “Antage W-300” (Kawaguchi Kagaku Co.), “Irganox L-109” (Ciba Speciality Chemicals Co.), “Tominox 917” (Yoshitomi Seiyaku Co.), “Irganox L-115” (Ciba Speciality Chemicals Co.), “Sumilizer GA80” (Sumitomo Kagaku), “Antage RC” (Kawaguchi Kagaku Co.), “Irganox L-101” (Ciba Speciality Chemicals Co.), “Yoshinox 930” (Yoshitomi Seiyaku Co.).

The lubricating oil composition of the present invention may include mixtures of one or more phenolic antioxidants with one or more aminic antioxidants.

According to the present invention, the lubricating composition preferably includes up to about 30 wt % of a viscosity modifier, based on the total weight of the lubricating composition. In one embodiment, the lubricating composition comprises from 20 wt % to 30 wt % of a viscosity modifier. In another embodiment, the lubricating composition includes up to about 20 wt % of a viscosity modifier. In an alternate embodiment, the lubricating composition includes between about 10 and 20 wt % of a viscosity modifier. In yet another emobidment, the lubricating composition includes between about 1 and 10 wt % of a viscosity modifier. In a preferred embodiment of the present invention, the lubricating composition is essentially free of viscosity modifier. In a particularly preferred embodiment of the present invention, the lubricating composition comprises 0 wt % of a viscosity modifier.

Examples of viscosity index improvers include copolymers of alpha-olefins and dicarboxylic acid esters such as those described in U.S. Pat. No. 4,931,197. Commercially available copolymers of alpha-olefins and dicarboxylic acid diesters include the Ketjenlube polymer esters available from Italmatch (and previously Akzo Nobel Chemicals). Other suitable examples of viscosity index improvers are polyisobutylenes; commercially available polyisobutylenes include the Oloa® products (Chevron Oronite).

Further examples of viscosity index improvers which may conveniently be used in the lubricating compositions of the present invention include the styrene-butadiene stellate copolymers, styrene-isoprene stellate copolymers and the polymethacrylate copolymers and ethylene-propylene copolymers (also known as olefin copolymers) of the crystalline and non-crystalline type.

Suitable olefin copolymers include those commercially available under the trade designation “PARATONE®” (such as “PARATONE® 8921” and “PARATONE® 8941”) (Chevron Oronite Company LLC); those commercially available under the trade designation “HiTEC®” (such as “HiTEC® 5850B”) (Afton Chemical Corporation); and those commercially available under the trade designation “Lubrizol® 7067C” (The Lubrizol Corporation). Suitable polyisoprene polymers include those commercially available under the trade designation “SV200” (Infineum International Ltd.). Suitable diene-styrene copolymers include those commercially available under the trade designation “SV 260” (Infineum International Ltd).

The compositions herein may also include one or more anti-wear additives. Suitable anti-wear additives for use herein include zinc dithiophosphate compounds selected from zinc dialkyl-, diaryl- and/or alkylaryl-dithiophosphates, molybdenum-containing compounds, and ashless anti-wear additives such as substituted or unsubstituted thiophosphoric acids, and salts thereof.

Examples of ashless thiophosphates are known in the art. These compounds are metal-free organic compounds. Suitable ashless thiophosphates for use in the lubricating oil composition of the present invention may include esters and/or salts of thiophosphoric acids, and substituted thiophosphoric acids. Preferably, the ashless thiophosphates are substituted by one or more hydrocarbyl groups which hydrocarbyl groups can optionally contain an acid, a hydroxy and/or an ester group. The hydrocarbyl moiety preferably is an alkyl group containing up to 12 carbon atoms. The hydrocarbyl-substituted thiophosphate preferably contains 2 or 3 hydrocarbyl groups, or is a mixture of thiophosphates containing 2 and 3 hydrocarbyl groups.

The ashless thiophosphates can contain any number of sulphur atoms directly linked to the phosphorus atom. Preferably, the thiophosphates are monothiophosphates and/or dithiophosphates.

Examples of ashless thiophosphates which may be conveniently used in the lubricating oil composition of the present invention are described in EP-A-0375324, U.S. Pat. Nos. 5,922,657, 4,333,841 and 5,093,016, and may be conveniently made according to the methods described therein.

Examples of commercially available ashless thiophosphates that may be conveniently used in the lubricating oil composition of the present invention include those available under the trade designations “IRGALUBE L-63” and “IRGALUBE 353” (Ciba Specialty Chemicals) and that available under the trade designation “LZ 5125” (Lubrizol).

In certain embodiments, the lubricating composition can include one or more anti-wear additives selected from one or more zinc dithiophosphates. The or each zinc dithiophosphate may be selected from zinc dialkyl-, diaryl- or alkylaryl-dithiophosphates.

Examples of zinc dithiophosphates which are commercially available include those available under the trade designations “Lz 677A”, “Lz 1095”, “Lz 1097”, “Lz 1370”, “Lz 1371”, “Lz 1373” and “Lz 1395” (Lubrizol Corp.), those available under the trade designations “OLOA 260”, “OLOA 262”, “OLOA 267” and “OLOA 269R” (Chevron Oronite), and those available under the trade designation “HITEC 7169” and “HITEC 7197” (Afton Chemical).

Preferably, the lubricating composition according to the present invention includes a phosphorus containing compound, preferably selected from the group consisting of phosphonates, phosphates, phosphites, phosphorothionates and dithiophosphates, and combinations thereof. Examples of commercially available dithiophosphates and phosphates are “IRGALUBE 63” and IRGALUBE 349”, respectively, both available from Ciba Specialty Chemicals.

The lubricating oil composition of the present invention has a kinematic viscosity at 40° C. in the range of from 2 mm²/s to 220 mm2/s, preferably in the range of from 32 mm²/s to 220 mm²/s.

In addition to the components mentioned above, the lubricating composition according to the present invention may further include one or more additional additives such as anti-oxidants, dispersants, detergents, extreme-pressure additives, friction modifiers, viscosity index improvers, pour point depressants, metal passivators, corrosion inhibitors, demulsifiers, anti-foam agents, seal compatibility agents and additive diluent base oils, etc.

As the person skilled in the art is familiar with the above and other additives, these are not further discussed here in detail.

Specific examples of such additives are described in for example Kirk-Othmer Encyclopedia of Chemical Technology, third edition, volume 14, pages 477-526.

The above-mentioned additives are typically present in an amount in the range of from 0.01 to 35.0 wt. %, based on the total weight of the lubricating composition, preferably in an amount in the range of from 0.05 to 25.0 wt. %, more preferably from 0.1 to 20.0 wt. %, based on the total weight of the lubricating composition.

The lubricating compositions of the present invention may be conveniently prepared by admixing the one or more additives with the base oil(s).

The lubricating composition according to the present invention may be used in various applications, such as a transmission oil, a grease, a hydraulic oil, an industrial gear oil, a turbine oil, a compressor oil, and the like.

In another aspect, the present invention provides a method for improving one or more of oxidation stability and deposit reduction properties, which method includes lubricating with a lubricating composition according to one aspect of the invention. In another aspect, the present invention provides the use of a lubricating composition as described herein, for improving one or more of oxidation stability properties (for example, as determined by ASTM D6186-98) and deposit reduction properties (for example, as determined according to ASTM D7097-09 or JPI-5S-55-99).

In another aspect, the present invention provides a method for improving foam performance, generally defined as a lower propensity of the lubricant composition to form foam, and a less stable foam upon formation (as determined by ASTM D892). Similarly, in another aspect, the present invention provides a method for improving air release, generally defined as a lower propensity of the lubricant composition to retain air, and generally retaining air for a shorter amount of time. In another aspect, the present invention provides a method for improving demulsibility, generally defined as the lowering the propensity of the lubricant composition to form stable emulsions. The demulsibility is typically measured by the ability of a mixture of the lubricant composition and water to form two separate layers. In alternate embodiments, the present invention provides a method for improving the filterability of the lubricant composition, wherein the improved filterability is demonstrated by a lower potential of the lubricant composition to block or plug filtration media.

The present invention is described below with reference to the following Examples, which are not intended to limit the scope of the present invention in any way.

EXAMPLES Lubricating Oil Compositions

Various combinations of additives, base oils and solvency boosters were formulated. Table 1 shows the properties of the base oils.

“Base oil 1” (or “BO1” or “GTL 4”) was a Fischer-Tropsch derived base oil having a kinematic viscosity at 100° C. (ASTM D445) of approximately 3.89 cSt (mm²s⁻¹). Base oil 1 may be conveniently manufactured by the process described in e.g. WO-A-02/070631, the teaching of which is hereby incorporated by reference.

“Base oil 2” (or “BO2”) was a commercially available Group III base oil having a kinematic viscosity at 100° C. (ASTM D445) of approximately 4.3 cSt. Base oil 2 is commercially available from e.g. SK Energy (Ulsan, South Korea) under the trade designation Yubase 4.

“Base oil 3” or (GTL 3) was a Fischer-Tropsch derived base oil having having a kinematic viscosity at 100° C. (ASTM D445) of approximately 2.700 cSt (mm²s⁻¹). Base oil 3 may be conveniently manufactured by the process described in e.g. WO-A-02/070631, the teaching of which is hereby incorporated by reference.

“Base oil 4” or (GTL 8) was a Fischer-Tropsch derived base oil having having a kinematic viscosity at 100° C. (ASTM D445) of approximately 4.000 cSt (mm²s⁻¹). Base oil 4 may be conveniently manufactured by the process described in e.g. WO-A-02/070631, the teaching of which is hereby incorporated by reference.

TABLE 1 Base Base oil 2 Base oil 1 (Yubase oil 3 Base oil 4 (GTL 4) 4) (GTL 3) (GTL 8) Kinematic viscosity at 16.91 19.49 9.930 43.51 40° C.¹ [cSt] Kinematic viscosity at 3.89 4.3 2.707 7.613 100° C.¹ [cSt] VI Index² 127 126 112 144 Pour point³ [° C.] −39 −18 −39 −21 Noack volatility⁴ [wt. %] 11.2 14.2 46.8 2.1 Saturates⁵ [wt. %] 99.2 99.3 99.9 99.9 Tertiary Carbon, %⁶ 18.1 n.d. n.d. n.d. Secondary Carbon, %⁶ 66.7 n.d. n.d. n.d. Primary Carbon, %⁶ 14.3 n.d. n.d. n.d. Epsilon carbon content, %⁶ 12.1 n.d. n.d. n.d. n- and iso-paraffins⁷ 92.35 n.d. n.d. n.d. Mono-naphthenics⁷ 6.85 n.d. n.d. n.d. di- and poly-naphthenics⁷ 0.87 n.d. n.d. n.d. Aromatics⁵ 0.5 n.d. n.d. n.d. Dynamic viscosity at −20° C.⁸ n.d. 713 n.d. n.d. [cP] Dynamic viscosity at −25° C.⁸ n.d. 931 n.d. n.d. [cP] Dynamic viscosity at −30° C.⁸ 948 n.d. n.d. 5010 [cP] Dynamic viscosity at −35° C.⁸ 1580 n.d. n.d. 9340 [cP] ¹According to ASTM D 445 ²According to ASTM D 2270 ³According to ASTM D 5950 ⁴According to CEC L-40-A-93/ASTM D 5800 ⁵According to IP 368 (modified) ⁶According to 13C NMR ⁷According to FIMS ⁸According to ASTM D 5293 n.d. = not determined

HPDSC-OIT Test

In order to measure the oxidation stability properties of the various lubricating compositions set out in Table 2, the lubricating compositions were subjected to the HPDSC-OIT (High Pressure Differential Scanning calorimetry) test according to ASTM D6186-08, at a temperature of 200° C., and oxygen at 200 psig).

Improved anti-oxidation properties are evidenced by greater oxidation induction time (OIT).

Foaming Performance

In order to measure the foaming performance, the lubricating compositions were subjected to a foaming test according to ASTM D892.

Air Release

In order to measure the air release performance, the lubricating compositions were subjected to an air release test according to ASTM D3427.

Results

Samples were prepared that included mineral (Yubase 4) and synthetic (GTL4) base oils and between 0.0001 and 0.001 wt. % of the dyes.

Results show the lubricant compositions of the present invention which include GTL4 and Unisol high flash organic dye show improved oxidative stability, as measured according to ASTM D6186-08, relative to similar lubricant compositions that include mineral base oils. Furthermore, the GTL4 base oil lubricants having Unisol high flash organic dye unexpectedly show a non-linear relationship with respect to the oxidative stability and the amount of dye present in the lubricant formulation. Samples having Unisol high flash organic dye compounds present require reduced amounts of anti-oxidants than do either lubricant compositions that either do not include organic dye compounds or lubricant compositions that include organic dye compounds and a mineral base oil.

The lubricant compositions of the present invention also show improved foaming performance, relative to similar compositions having a mineral base oil. Compositions that include both a GTL base oil and Unisol high flash organic dye compound unexpectedly show reduced foaming, and less stable foam volume values, as compared with similar mineral base oils. In certain embodiments, lubricant compositions having a concentration of Unisol high flash organic dye of 0.0005 wt. % showed a reduction in the amount of foam produced.

Lubricant compositions of the present invention also show improved air release, as demonstrated by a shorter air release time, relative to those lubricant compositions that do not include organic dye compounds or a GTL base oil. For example, compounds of the present invention having both a GTL base oil and Unisol high flash organic dye compound at a concentration of 0.0005 wt. % exhibit air release times that are lower than similar compositions that do not include organic dye compounds. 

I claim:
 1. A lubricating oil composition comprising: (a) a base oil comprising a Fischer-Tropsch derived base oil; and (b) an organic dye compound.
 2. The lubricating oil composition according to claim 1, wherein the organic dye compound comprises an organic dye dissolved in a hydrocarbon solvent or petroleum distillate.
 3. The lubricating oil composition according to claim 1, wherein the the organic dye compound is present in an amount of between about 0.0001 and 0.001% by weight of the lubricant composition.
 4. The lubricating oil composition according to claim 2, wherein the organic dye is dissolved in kerosene.
 5. The lubricating oil composition according to claim 2, wherein the hydrocarbon solvent is selected from xylene, dimethylbenzene, and ethylbenzene.
 6. The lubricating oil composition according to claim 1, wherein the organic dye compound is a low flash dye.
 7. The lubricating oil composition according to claim 1, wherein the organic dye compound is a high flash dye.
 8. A lubricating oil composition according to any of claims 1 to 8 wherein the Fischer-Tropsch derived base oil has a kinematic viscosity at 100° C. of from 1 mm²/s to 35 mm²/s.
 9. A lubricating oil composition according to any of claims 1 to 8 wherein the base oil contains more than 50 wt. %, preferably more than 60 wt. %, more preferably more than 70 wt. %, even more preferably more than 80 wt. %, most preferably more than 90 wt. % Fischer-Tropsch derived base oil.
 10. Use of a lubricating oil composition according to any of claims 1 to 8 for providing improved anti-oxidation properties, as determined by ASTM D6186-08.
 11. Use of a lubricating oil composition according to any of claims 1 to 8 for providing improved deposit reduction properties, as determined according to ASTM D7097-09 or JPI-5S-55-99.
 12. Use of a lubricating oil composition according to any of claims 1 to 8 for providing improved foaming performance.
 13. Use of a lubricating oil composition according to any of claims 1 to 8 for providing improved air release.
 14. A method for lubricating a, the method comprising the step of lubricating said engine with the oil composition of any of claims 1-8, wherein the step of lubricating the engine results in a reduction of the amount of oxidation products that are formed.
 15. A method for lubricating an engine, the method comprising the step of lubricating said engine with the oil composition of any of claims 1-8, wherein the step of lubricating the engine results in a reduction in the amount of deposits that are formed.
 16. A method for lubricating an engine, the method comprising the step of lubricating said engine with the oil composition of any of claims 1-8, wherein the step of lubricating the engine results in improved foaming performance.
 17. A method for lubricating an engine, the method comprising the step of lubricating said engine with the oil composition of any of claims 1-8, wherein the step of lubricating the engine results in improved air release. 